What I did on my 280E was to have the auto and manual flywheel statically balanced by a machine shop. You mark the crank flange and the auto flywheel and remove it. You then take the flywheels to the machine shop. They will balance them, removing from or adding some metal to the manual one, and give them back to you with a mark on the manual one that you line up with the mark on the crank flange when you install it.

If you can't find a shop in your area, Metric Motors in LA does it all the time.

Cost like $50 and it was smooth as silk.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe